Master-slave data transmission systems employing a single-wire bus are known in the prior art and include control systems having a single data channel. See, for example, European Patent Application Number 0315158, filed on Nov. 2, 1988 and published May 10, 1989 in Bulletin 89/19, entitled METHOD AND APPARATUS FOR CONTROLLING TERMINALS ON A COMMUNICATION NETWORK by Ueno, Reiko and assigned to Matsushita Electric Co., U.S. Pat. No. 4,438,491 issued Mar. 20, 1984, entitled COMPUTER HAVING PLURAL IC CHIPS WITH EACH CHIP INCLUDING A TRANSCEIVER by J. N. Constant, an article entitled HOMENET: A CONTROL NETWORK FOR CONSUMER APPLICATIONS, IEEE Transactions on Consumer Electronics, Vol. CE-29 (1983), No. 3 (297-304) by F. W. Gutzwiller et al. and article entitled A DIGITAL DATA BUS FOR SMALL AREA NETWORKS by T. Danbury, New Electronics, April, 1984 pp. 27-33. These materials show various data transmission systems and many of which employ two wire techniques for operation and are of general interest to the present system. See EPA 0217571 entitled DATA TRANSFER COMMUNICATION SYSTEM, filed Sep. 10, 1986 by R. D. Crawford et al. and assigned to Ford Motor Company, EPA 0069509 filed Jun. 23, 1982, entitled A CIRCUIT FOR READING OUT ADDRESS DATA APPLIED TO A MEMORY IN A ONE-CHIP MICROCOMPUTER by S. Masaki. These patents show a plurality of terminals of a communication network connected to a transmission line to communicate mutually. Each terminal includes a single device or multiple devices. There is an address assigned to each terminal with each terminal having a device address, a subdevice address assigned to respective devices constituting each terminal and having a single or a plurality of values, and a function address assigned to respective functions possessed by each device, whereby when a terminal to be controlled is a multiple device, only a desired function is controlled. If two or more masters and/or two or more slaves are present, collision-free control of the single-wire bus requires a complex control circuit. The cost of such a control circuit is warranted only if additional bus and control lines must be avoided because of the distance. Progress in integrated circuit technology, particularly in monolithic integrated circuit technology, makes it possible to provide system components previously implemented as passive devices with "electronic intelligence". This offers great advantages in data transmission systems where distance is not particularly critical.
It is an object of the present invention to provide a master-slave data transmission system operating with a single-wire bus which permits multiple-master and slave operation using a data format that can be simply adapted to the respective transmission and operational requirements.